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Re: recent AO-40 efforts?



Hi Don and Auke,

> I believe AO-40 was designed by AMSAT to not allow both sets of batteries to
> be disconnected. We should have learned with AO-7 that every satellite
> should be able to work on solar power alone as eventually all batteries will
> fail. It is my understanding that the only chance we have is if the
> batteries burn open some day in the future.
>   
This is not the problem...  you can not compare a spacecraft like AO-7 
with Phase 3 satellites...

AO-40 would not work just from solar power and without batteries. 
The battery works as big capacitor for the transponders. In mean, the 
power budget would be positive, but during high peak on the transponder 
due to load, the transponder would drain current from the battery as the 
peak power would not be sufficient for the generated power from the 
solar cells.  Without the battery, the transponder would be very 
unstable as the voltage breaks down. And even worse, the voltage break 
down would cause the IHU (onboard computer) to make a power down reset.
So we could probably only have telemetry beacon, nothing else...
During each eclipse pass, sometimes every orbit, the computer would also 
reset again and again.
Since all the software must be reloaded from ground, this is a task we 
could not provide every day.
But without computer, we would quickly loose orientation of the 
spacecraft and thus, the solar panelsl would quickly point away from the 
sun.. and that's is it..
Look at AO-10 to understand what I mean..
AO-40 was never designed to work without battery and this would also 
make totally no sense..
The problem was, that the Main Battery died so quickly in a totally 
catastrophic failure, which no one could have foreseen.
Time for the command stations was too short to charge the Auxiliary 
Battery and do the switch over...

Command stations have tried to send command to the spacecraft since the 
battery failure, but the rate of these attempts decreased over the last 
couple of years.
We at AMSAT-DL currently plan to make a new attempt using our 20m dish 
from Bochum. There we would have a lot of power and very good ears too..
However, I can not give an exact date when the will happen.  Also it may 
need several weeks of attempts, since the attitude of AO-40 in regard to 
the sun is unknown.
If we try at the wrong time, the solar cells may not generate any power 
due to bad sun angle..

We will indeed keep you all informed when we do our first try to recover 
AO-40 from Bochum...

73s Peter

BTW:  Are there still people listening for AO-10?



> -----Original Message-----
> From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On
> Behalf Of Auke de Jong, VE6PWN
> Sent: Saturday, March 01, 2008 7:53 PM
> To: AMSAT-BB
> Subject: [amsat-bb] recent AO-40 efforts?
>
> I noticed that during the last period of documented efforts to recover AO-40
> 4 years ago, there were promising results about hearing faint signals.  By
> my interpretation of those old reports, they basically confirmed that the
> command receiver was working but could not get much else done with it.  Now
> that it has been officially silent for several years, has anyone tried to
> send commands to it in order to disconnect the (shorted) battery banks via
> the relays onboard?  Given the changing sun-angles on the arrays and the
> passage of time, as well as possible heating of certain onboard components
> due to the constant supply of solar power to the shorted batteries, could
> there be any possibility of (energizing) the battery-disconnect relays?  I
> presume that they are in a fail-close arrangement, because if they were
> fail-open, they should have already done-so due to the shunted power system.
> Also, could the solar panels have fuses that have opened?  could such fuses
> be re-settable?
>
> I would be interested to hear what knowledge there exists about the present
> status of AO-40, especially what "google" couldn't fetch.
>
> Auke de Jong
> VE6PWN
> DO33go
> Edmonton, AB
>
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> _______________________________________________
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>   

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